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Linux/net/netfilter/ipvs/ip_vs_dh.c

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  1 /*
  2  * IPVS:        Destination Hashing scheduling module
  3  *
  4  * Authors:     Wensong Zhang <wensong@gnuchina.org>
  5  *
  6  *              Inspired by the consistent hashing scheduler patch from
  7  *              Thomas Proell <proellt@gmx.de>
  8  *
  9  *              This program is free software; you can redistribute it and/or
 10  *              modify it under the terms of the GNU General Public License
 11  *              as published by the Free Software Foundation; either version
 12  *              2 of the License, or (at your option) any later version.
 13  *
 14  * Changes:
 15  *
 16  */
 17 
 18 /*
 19  * The dh algorithm is to select server by the hash key of destination IP
 20  * address. The pseudo code is as follows:
 21  *
 22  *       n <- servernode[dest_ip];
 23  *       if (n is dead) OR
 24  *          (n is overloaded) OR (n.weight <= 0) then
 25  *                 return NULL;
 26  *
 27  *       return n;
 28  *
 29  * Notes that servernode is a 256-bucket hash table that maps the hash
 30  * index derived from packet destination IP address to the current server
 31  * array. If the dh scheduler is used in cache cluster, it is good to
 32  * combine it with cache_bypass feature. When the statically assigned
 33  * server is dead or overloaded, the load balancer can bypass the cache
 34  * server and send requests to the original server directly.
 35  *
 36  */
 37 
 38 #define KMSG_COMPONENT "IPVS"
 39 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
 40 
 41 #include <linux/ip.h>
 42 #include <linux/slab.h>
 43 #include <linux/module.h>
 44 #include <linux/kernel.h>
 45 #include <linux/skbuff.h>
 46 
 47 #include <net/ip_vs.h>
 48 
 49 
 50 /*
 51  *      IPVS DH bucket
 52  */
 53 struct ip_vs_dh_bucket {
 54         struct ip_vs_dest __rcu *dest;  /* real server (cache) */
 55 };
 56 
 57 /*
 58  *     for IPVS DH entry hash table
 59  */
 60 #ifndef CONFIG_IP_VS_DH_TAB_BITS
 61 #define CONFIG_IP_VS_DH_TAB_BITS        8
 62 #endif
 63 #define IP_VS_DH_TAB_BITS               CONFIG_IP_VS_DH_TAB_BITS
 64 #define IP_VS_DH_TAB_SIZE               (1 << IP_VS_DH_TAB_BITS)
 65 #define IP_VS_DH_TAB_MASK               (IP_VS_DH_TAB_SIZE - 1)
 66 
 67 struct ip_vs_dh_state {
 68         struct ip_vs_dh_bucket          buckets[IP_VS_DH_TAB_SIZE];
 69         struct rcu_head                 rcu_head;
 70 };
 71 
 72 /*
 73  *      Returns hash value for IPVS DH entry
 74  */
 75 static inline unsigned int ip_vs_dh_hashkey(int af, const union nf_inet_addr *addr)
 76 {
 77         __be32 addr_fold = addr->ip;
 78 
 79 #ifdef CONFIG_IP_VS_IPV6
 80         if (af == AF_INET6)
 81                 addr_fold = addr->ip6[0]^addr->ip6[1]^
 82                             addr->ip6[2]^addr->ip6[3];
 83 #endif
 84         return (ntohl(addr_fold)*2654435761UL) & IP_VS_DH_TAB_MASK;
 85 }
 86 
 87 
 88 /*
 89  *      Get ip_vs_dest associated with supplied parameters.
 90  */
 91 static inline struct ip_vs_dest *
 92 ip_vs_dh_get(int af, struct ip_vs_dh_state *s, const union nf_inet_addr *addr)
 93 {
 94         return rcu_dereference(s->buckets[ip_vs_dh_hashkey(af, addr)].dest);
 95 }
 96 
 97 
 98 /*
 99  *      Assign all the hash buckets of the specified table with the service.
100  */
101 static int
102 ip_vs_dh_reassign(struct ip_vs_dh_state *s, struct ip_vs_service *svc)
103 {
104         int i;
105         struct ip_vs_dh_bucket *b;
106         struct list_head *p;
107         struct ip_vs_dest *dest;
108         bool empty;
109 
110         b = &s->buckets[0];
111         p = &svc->destinations;
112         empty = list_empty(p);
113         for (i=0; i<IP_VS_DH_TAB_SIZE; i++) {
114                 dest = rcu_dereference_protected(b->dest, 1);
115                 if (dest)
116                         ip_vs_dest_put(dest);
117                 if (empty)
118                         RCU_INIT_POINTER(b->dest, NULL);
119                 else {
120                         if (p == &svc->destinations)
121                                 p = p->next;
122 
123                         dest = list_entry(p, struct ip_vs_dest, n_list);
124                         ip_vs_dest_hold(dest);
125                         RCU_INIT_POINTER(b->dest, dest);
126 
127                         p = p->next;
128                 }
129                 b++;
130         }
131         return 0;
132 }
133 
134 
135 /*
136  *      Flush all the hash buckets of the specified table.
137  */
138 static void ip_vs_dh_flush(struct ip_vs_dh_state *s)
139 {
140         int i;
141         struct ip_vs_dh_bucket *b;
142         struct ip_vs_dest *dest;
143 
144         b = &s->buckets[0];
145         for (i=0; i<IP_VS_DH_TAB_SIZE; i++) {
146                 dest = rcu_dereference_protected(b->dest, 1);
147                 if (dest) {
148                         ip_vs_dest_put(dest);
149                         RCU_INIT_POINTER(b->dest, NULL);
150                 }
151                 b++;
152         }
153 }
154 
155 
156 static int ip_vs_dh_init_svc(struct ip_vs_service *svc)
157 {
158         struct ip_vs_dh_state *s;
159 
160         /* allocate the DH table for this service */
161         s = kzalloc(sizeof(struct ip_vs_dh_state), GFP_KERNEL);
162         if (s == NULL)
163                 return -ENOMEM;
164 
165         svc->sched_data = s;
166         IP_VS_DBG(6, "DH hash table (memory=%zdbytes) allocated for "
167                   "current service\n",
168                   sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE);
169 
170         /* assign the hash buckets with current dests */
171         ip_vs_dh_reassign(s, svc);
172 
173         return 0;
174 }
175 
176 
177 static void ip_vs_dh_done_svc(struct ip_vs_service *svc)
178 {
179         struct ip_vs_dh_state *s = svc->sched_data;
180 
181         /* got to clean up hash buckets here */
182         ip_vs_dh_flush(s);
183 
184         /* release the table itself */
185         kfree_rcu(s, rcu_head);
186         IP_VS_DBG(6, "DH hash table (memory=%zdbytes) released\n",
187                   sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE);
188 }
189 
190 
191 static int ip_vs_dh_dest_changed(struct ip_vs_service *svc,
192                                  struct ip_vs_dest *dest)
193 {
194         struct ip_vs_dh_state *s = svc->sched_data;
195 
196         /* assign the hash buckets with the updated service */
197         ip_vs_dh_reassign(s, svc);
198 
199         return 0;
200 }
201 
202 
203 /*
204  *      If the dest flags is set with IP_VS_DEST_F_OVERLOAD,
205  *      consider that the server is overloaded here.
206  */
207 static inline int is_overloaded(struct ip_vs_dest *dest)
208 {
209         return dest->flags & IP_VS_DEST_F_OVERLOAD;
210 }
211 
212 
213 /*
214  *      Destination hashing scheduling
215  */
216 static struct ip_vs_dest *
217 ip_vs_dh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
218                   struct ip_vs_iphdr *iph)
219 {
220         struct ip_vs_dest *dest;
221         struct ip_vs_dh_state *s;
222 
223         IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
224 
225         s = (struct ip_vs_dh_state *) svc->sched_data;
226         dest = ip_vs_dh_get(svc->af, s, &iph->daddr);
227         if (!dest
228             || !(dest->flags & IP_VS_DEST_F_AVAILABLE)
229             || atomic_read(&dest->weight) <= 0
230             || is_overloaded(dest)) {
231                 ip_vs_scheduler_err(svc, "no destination available");
232                 return NULL;
233         }
234 
235         IP_VS_DBG_BUF(6, "DH: destination IP address %s --> server %s:%d\n",
236                       IP_VS_DBG_ADDR(svc->af, &iph->daddr),
237                       IP_VS_DBG_ADDR(dest->af, &dest->addr),
238                       ntohs(dest->port));
239 
240         return dest;
241 }
242 
243 
244 /*
245  *      IPVS DH Scheduler structure
246  */
247 static struct ip_vs_scheduler ip_vs_dh_scheduler =
248 {
249         .name =                 "dh",
250         .refcnt =               ATOMIC_INIT(0),
251         .module =               THIS_MODULE,
252         .n_list =               LIST_HEAD_INIT(ip_vs_dh_scheduler.n_list),
253         .init_service =         ip_vs_dh_init_svc,
254         .done_service =         ip_vs_dh_done_svc,
255         .add_dest =             ip_vs_dh_dest_changed,
256         .del_dest =             ip_vs_dh_dest_changed,
257         .schedule =             ip_vs_dh_schedule,
258 };
259 
260 
261 static int __init ip_vs_dh_init(void)
262 {
263         return register_ip_vs_scheduler(&ip_vs_dh_scheduler);
264 }
265 
266 
267 static void __exit ip_vs_dh_cleanup(void)
268 {
269         unregister_ip_vs_scheduler(&ip_vs_dh_scheduler);
270         synchronize_rcu();
271 }
272 
273 
274 module_init(ip_vs_dh_init);
275 module_exit(ip_vs_dh_cleanup);
276 MODULE_LICENSE("GPL");
277 

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